A wide variety of medical devices are used for delivering a therapy or monitoring a physiological condition related to a cardiac health within a patient. For example, implantable medical devices, such as cardiac pacemakers or implantable cardioverter defibrillators, provide therapeutic stimulation to the heart by delivering electrical therapy signals, such as pulses for pacing, or shocks for cardioversion or defibrillation. In some cases, such an implantable medical device (IMD) may sense for intrinsic depolarizations of the heart, and control the delivery of such signals to the heart based on the sensing.
In some cases, an IMD device includes sensors for detecting heart sounds signals in addition to electrical signals. As described in Published U.S. Patent Application 2010/0331903 to Zhang et al. entitled “HEART SOUND SENSING TO REDUCE INAPPROPRIATE TACHYARRHYTHMIA THERAPY,” incorporated herein by reference in its entirety, heart sounds signals are detected and used to determine whether the heart sounds are normal or abnormal. The heart sounds may also be used to confirm or reject an indication that therapy may be needed based on electrical signals.
Heart failure is a condition affecting thousands of people worldwide. Essentially, congestive heart failure occurs when the heart is unable to pump blood at an adequate rate in response to the filling pressure. A worsening heart failure condition may result in symptoms such as congestion in the tissue, peripheral edema, pulmonary edema, and shortness of breath, and coughing. When heart failure is severe, it can even lead to patient death.
Pulmonary hypertension is abnormally high blood pressure in the arteries of the lungs. The right side of the heart of a patient with pulmonary hypertension must work harder than normal to provide an adequate blood supply to the lungs. In patients with pulmonary hypertension the blood vessels of the lungs have narrowed causing pressure build up. The extra work the heart must do to force the blood through the vessels can result in an enlarging of the right side of the heart. This may eventually result in heart failure in the right side of the heart.